A wide variety of antigens stimulate the production of antibodies in animals and confer protection against subsequent infection. However, some antigens are unable to stimulate an effective immune response.
The immunogenicity of a relatively weak antigen is often enhanced by the simultaneous administration of the antigen with an adjuvant, a substance that is not immunogenic when administered alone, but will induce a state of mucosal and/or systemic immunity when combined with the antigen. Unfortunately, many immunoadjuvants, such as Freund's Complete Adjuvant, are toxic and are therefore only useful for animal research purposes, not human vaccinations.
Ionically cross-linkable water soluble polymers, poly[di(carboxylatophenoxy)phosphazene]s (PCPPs) have been developed (Allcock, H. R. and S. Swan, Macromolecules, 22:75-79 (1989)). In the soluble state, PCPP has been demonstrated to have adjuvant activity (U.S. Pat. No. 5,494,673) and has enhanced the immunogenicity of various antigens (Payne, L. G. et al., Vaccine, 16:92-98(1998)). Generally, the addition of PCPP to antigen preparations has enhanced functional hemagglutination inhibition (HAI) antibody response and has enhanced IgM, IgG, and IgG1 ELISA antibody titers over the levels elicited by vaccine alone. PCPP as an adjuvant has been demonstrated to be as efficient as or to outperform complete Freund's adjuvant. The immunogenicity of antigens as diverse as tetanus toxoid, hepatitis B surface antigen, Hemophilus influenzae type b polyribosribotolphosphate, herpes simplex virus type 2 glycoprotein D and HIV env has been dramatically enhanced in the presence of soluble PCPP (Payne, L. G. et al., Modulation of the Immune Response to Vaccine Antigens, Lars Haaheim, ed, Geneva (1997); Lu, Y. et al., J. AIDS Human Retrovirol., 12:99-106 (1996)).